The present invention relates to a multimedia data decoder for decoding a bit stream of coded multimedia data (audio/image data) according to a predetermined standard.
Standards called MPEG1, MPEG2 and MPEG4 (moving picture experts group phase 1, 2 and 4), the standards named after the experts group of ISO (international organization for standardization), are conventionally well known in the art as compression standards of multimedia data. MP3 (MPEG audio layer 3) is one of the audio compression methods used in MPEG1. On the other hand, MPEG2 is used in a currently used DVD (digital versatile disk) player.
The technology disclosed in Japanese Laid-Open Publication No. 8-116314 relates to decoding of an MPEG1 audio bit stream in the second-generation EDTV (enhanced definition television), EDTV-II. According to this technology, even if an error is generated in header information of a certain audio frame within a transmission system, generation of noises due to the error is suppressed. Such suppression of noise generation is achieved as follows: if any error is detected, bit information common to header information of the MPEG1 audio bit stream is extracted from control bits of an EDTV-II digital audio format and the header information of the MPEGI audio bit stream is modified based on the extracted bit information. Thereafter, coded data in the audio frame is decoded.
Recently, many users compress music data into an MP3 format by a personal computer or the like in order to store the music data in a disk. Since the disk thus produced does not completely meet the standard of a DVD player, some troubles may occur upon reproduction of the disk by the DVD player. For example, if sampling frequency information in a certain audio frame has an out-of-standard value, a value that is not defined by the standard, coded data in this audio frame is not decoded. This results in discontinuity of sound during reproduction by the DVD player, and in the worst case, no sound may be output.